1. Technical Field
The present disclosure relates to a mobile communication terminal and a case cover that is attachable to the mobile communication terminal.
2. Description of Related Art
Satellite cell-phone services for performing communication with a geostationary satellite arranged in the zenith direction by using a mobile communication terminal have been running. A high-gain antenna having directivity in the zenith direction is required for the satellite communication services. A linearly polarized wave is generally used for terrestrial wireless communication. On the other hand, in the satellite communication, a polarized wave direction is changed according to an attitude of a satellite, and hence, reception becomes difficult. Therefore, a clockwise circularly polarized wave has widely been used. Accordingly, an antenna of a satellite mobile terminal is demanded to be adapted to a clockwise circularly polarized wave and have a high gain in the zenith direction. On the other hand, an antenna for a terrestrial communication network is demanded to have uniformly a high gain in the substantially horizontal direction rather than in the zenith direction. Therefore, an antenna configuration adapted to both the terrestrial communication network and the satellite communication is difficult.
Japanese Translation of PCT Publication No. 2005-521289, Japanese Patent No. 4,173,453, and Japanese Patent No. 4,444,215 disclose a technique of switching directivity by improving an antenna (feeding element) or the like.
Japanese Translation of PCT Publication No. 2005-521289 discloses a mobile phone handset including at least one passive antenna element (parasitic) and one active antenna element (feeding element) adjacent to the passive antenna element protruding from a housing, wherein a circuit element (reactance element) is connected to the passive antenna element, and a constant of the circuit element is changed to change directivity. Further, Japanese Patent No. 4,173,453 discloses an antenna apparatus that changes capacitance of at least one of a feeding element provided on a dielectric substrate and having a length of λ/4, parasitic elements, which are provided on both sides of the feeding element, include a variable reactance element, and are configured of one or more slots, and the variable reactance element, so as to switch directivity. In addition, Japanese Patent No. 4,444,215 discloses a mobile wireless device and an antenna unit provided in the mobile wireless device, including a parasitic element at a position facing a dipole antenna, the parasitic element being provided such that the relation of m>k is established, where k is a distance of a straight line linking the center point of the dipole antenna and a point on the parasitic element facing the center point, and m is a distance of a straight line linking one end of the parasitic element and a point of the dipole antenna facing this one end. With this configuration, directivity in the direction opposite to an obstacle such as a human body can be obtained, and hence, a high gain can be achieved.